One of the conductive compositions of interest in the present invention is an electrically conductive coating material. Such an electrically conductive coating material is used for forming an electrode of an electronic element such as a monolithic ceramic capacitor. The electrically conductive coating material employed for such use contains an electrically conductive component comprising a powder of metal such as silver, copper, nickel, or palladium, which component is dispersed in a vehicle containing a solvent, a binder, and other components.
In the above-mentioned conductive coating material, the metal powder must be contained in a sufficiently dispersed state, and when the composition is applied onto an object to form a coating film, the resultant coating film must have a smooth surface with the metal being highly packed. If the metal powder is poorly dispersed, when an internal electrode of a monolithic ceramic capacitor, for example, is formed by use of the conductive coating material, the target capacitance decreases and values thereof are dispersed, and the equivalent series resistance increases disadvantageously.
When a metal powder assumes the form of a micropowder, such a powder typically forms aggregates. Therefore, in order to produce an electrically conductive coating material, the metal powder must be disintegrated to thereby be sufficiently dispersed in a vehicle.
In order to attain the above-mentioned requirements, an electrically conductive coating material is typically produced through the steps of kneading a metal powder and a vehicle containing a solvent, a binder, and other components by use of a kneader or a mixer and dispersing the metal powder in the vehicle by use of a three-roll mill or the like.
However, when the metal powder has a particle size of submicron order or smaller or the metal powder aggregates tightly, disintegrating the aggregated metal powder to a sufficient level through the above-described method so as to thoroughly disperse the powder in a vehicle is difficult. Therefore, in an electronic element having electrodes formed by use of such an electrically conductive composition, satisfactory characteristics are difficult to obtain.
In an alternative method, an electrically conductive coating material is produced through dispersing a metal powder in a vehicle by use of a mill employing a medium, such as a ball mill or a sand mill, instead of a three-roll mill or a like apparatus.
However, when the metal powder is dispersed through the above-described method, the metal powder collides with the medium to form an oblate spherical powder. When an electrically conductive coating material containing such an oblate spherical powder is used for forming an internal electrode of an element such as a monolithic ceramic capacitor, the oblate spherical powder serves as an unfavorable material in the coating film, to thereby adversely affect the reliability of the element; for example, the oblate spherical powder causes interlayer short circuits.
As described above, in a conventional process, disintegrating a metal powder to primary particles or nearly primary particles and sufficiently dispersing the powder in a vehicle has been difficult. Thus, an electronic element having an electrode formed by use of an electrically conductive coating material or an electrically conductive composition does not possess sufficient electric characteristics.
In view of the foregoing, the present invention provides a process for producing an electrically conductive composition which can solve the above-described problems, as well as an electrically conductive composition obtained through the process.